Cord blood
transplantation (CBT) is a distinct risk factor for human herpesvirus-6 (HHV-6) reactivation and HHV-6
encephalitis. In a prospective multicenter trial we investigated the effects of prophylactic
foscarnet (90 mg/kg i.v. infusion from days 7 to 27 after CBT) on the occurrence of HHV-6 reactivation, HHV-6
encephalitis, and acute
graft-versus-host disease (aGVHD) in CBT recipients. Between 2014 and 2016, 57 patients were included in a
foscarnet-prophylaxis group. Outcomes were compared with an historical control group who received CBT between 2010 and 2014 (standard-treatment group, n = 63). The cumulative incidence of high-level HHV-6 reactivation, defined as plasma HHV-6
DNA ≥ 104 copies/mL, at 60 days after CBT was significantly lower in the
foscarnet-prophylaxis group than in the standard-treatment group (18.3% versus 57.3%, P < .001). Multivariate analysis revealed that myeloablative preconditioning and standard treatment were significant risk factors for high-level HHV-6 reactivation. The cumulative incidence of HHV-6
encephalitis at 60 days after CBT was not different between the groups (
foscarnet-prophylaxis group, 12.4%; standard-treatment group, 4.9%; P = .14). The cumulative incidences of grades II to IV and grades III to IV aGVHD at 60 days after CBT were not different between the groups (grades II to IV aGVHD:
foscarnet-prophylaxis group, 42.0%; standard-treatment group, 40.5%; P = .96; grades III to IV aGVHD:
foscarnet-prophylaxis group, 14.5%; standard-treatment group, 14.5%; P = 1.00). In the setting of this study
foscarnet significantly suppressed systemic HHV-6 reactivation in CBT recipients but failed to prevent the development of HHV-6
encephalitis. Suppression of HHV-6 reactivation by
foscarnet did not show any effects against the incidence of aGVHD.